Small cell carcinoma of the brain without apparent extracranial origin in the same intracranial region one year following resection of malignant glioma.

Primary small cell carcinoma (SCC) of the brain is rare, and there have been no reports of small cell carcinoma located at the resection site of a glioma without extracranial tumours. Herein, we report a case of brain SCC in the same intracranial region from which a malignant glioma had been surgically resected a year prior. The patient, a 68-year-old male, had headaches as a symptom, and brain CT and MRI revealed a hyperdense region measuring 5.5×5 centimetres. Blood test results showed no significant changes. H&E staining suggested that these tumour cells had the characteristics of small cell lung carcinoma cells. Immunohistochemical staining for the glioma marker S100 was negative, but immunohistochemical staining for the neuroendocrine marker synaptophysin and for the cell adhesion molecule CD56 was strongly positive; meanwhile, staining for thyroid transcription factor-1 (TTF-1), a relatively specific marker of lung and thyroid carcinoma, was positive, and the Ki67 index was 75%. The pathological examination strongly suggested that the tumour was a small cell lung carcinoma, but CT and MRI scans indicated that there were no extracranial tumours. Hence, the tumour could be a primary small cell brain carcinoma. The patient underwent surgical resection again; the excised tumour was a mass of grey and white tissues with fragmentary morphology, and its dimensions were 3.0 cm×1.5 cm×0.8 cm.